The purpose of this study is to determine the safety and effectiveness of the SAPIEN XT™ THV with the associated delivery system for inoperable patients with severe symptomatic native aortic stenosis.

Cohort B was a 1:1 randomized, controlled study independently powered to compare transcatheter heart valve therapy with the first generation (SAPIEN™ THV) system to transcatheter heart valve therapy with the second generation (SAPIEN XT THV) system in patients who could not undergo surgery (inoperable).

Patients in the control arm of Cohort B received an Edwards SAPIEN THV with the associated delivery system while patients in the treatment arm of Cohort B received an Edwards SAPIEN XT THV with the associated delivery system.

Inclusion Criteria

1. Patient was symptomatic from his/her aortic valve stenosis, as demonstrated by NYHA Functional Class II or greater.
2. The probability of death or serious, irreversible morbidity is greater than or equal to 50%.
3. The heart team agreed (and verified in the case review process) that valve implantation would likely benefit the patient.
4. The study patient or the study patient's legal representative was informed of the nature of the study, agreed to its provisions and had provided written informed consent as approved by the Institutional Review Board (IRB) of the respective clinical site.
5. The study patient agreed to comply with all required post-procedure follow-up visits including annual visits through 5 years and analysis close date visits, which was conducted as a phone follow-up.

Exclusion Criteria

1. Aortic valve is a congenital unicuspid or congenital bicuspid valve, or is non-calcified.
2. Significant aortic disease, including marked tortuosity (hyperacute bend), aortic arch atheroma [especially if thick (> 5 mm), protruding or ulcerated] or narrowing (especially with calcification and surface irregularities) of the abdominal or thoracic aorta, severe "unfolding" and tortuosity of the thoracic aorta. (Transfemoral)
3. Currently participating in an investigational drug or another device study. Note: Trials requiring extended follow-up for products that were investigational, but have since become commercially available, are not considered investigational trials.
4. It is known that the patient is currently enrolled in the PARTNER I Trial or was withdrawn from the PARTNER I Trial prior to endpoint analysis.
5. Active bacterial endocarditis within 6 months (180 days) of procedure.